Google regularly replaces its logo on its search engine with special versions that are designed to celebrate anniversaries, but sometimes it comes up with something truly diverting. Friday’s “Google Doodle” provides one of those occasions.

It’s a celebration of the 44th anniversary of the birth of hip-hop, which Google places at DJ Kool Herc’s legendary emceeing session at a Bronx back-to-school party. Music historians have also pointed to earlier records as arguably containing...